1. Field of the Invention
The present invention relates to a single-lens reflex camera, and more particularly to a single-lens reflex camera for use with a photosensitive material having a large frame size such as an instant film.
2. Related Art
A single-lens reflex camera for use with monosheet type instant films is disclosed in JPA 3-123329. The monosheet type instant films, which enable one to see the result of photography immediately after the exposure, have a large frame size. The known single-lens reflex cameras have a Z-shaped optical path formed by a changeover mirror and a stationary mirror, so that a taking lens may be provided with a focal length long enough for the large instant film in a compact fashion. A conversion lens for the viewfinder is securely attached to the changeover mirror such that the changeover mirror may be inserted in the optical path of the taking lens concurrently with retraction of the conversion lens from the taking lens optical path without the need for a large space.
Because the changeover mirror must be moved at a high speed every exposure, a large power drive mechanism is necessary for swinging the mirror along with the heavy conversion lens at the high speed. Besides that, the high speed swinging movement of the mirror is suddenly stopped by the mirror striking against a stop. Therefore, a high stress is applied to the joint between the mirror and the conversion lens, so that the angle of the joint tends to change. Thus, the conventional mechanism has a problem of durability.
Moreover, in order to permit swinging of the changeover mirror, a slight gap is provided between the changeover mirror and a lens barrel of the taking lens when the changeover mirror is placed in the taking lens optical path. Therefore, light entering through an eyepiece of the viewfinder and traveling toward the changeover mirror may sometimes enter the photographic optical path through this gap, resulting in a reduced sharpness of the photographic image.